1. Technical Field
The present disclosure relates to a process control system, and more specifically, to improvements on communication through a network.
2. Related Art
In a process control system of the related art, a PC group having an operation monitoring function and the like and a controller are connected to each other through an independent control network so as realize a real-time property and high reliability.
FIG. 3 depicts a configuration of an example of the process control system of the related art. In FIG. 3, a field device 1 such as a sensor and an actuator is connected to a control network 3 via a controller 2.
A sensor 11 of the field device 1 is configured to measure a physical amount of a measurement target and an actuator 12 is configured to control the physical amount of the measurement target. The controller 2 is distributed and arranged in a plant and has a programmable calculation processing function for exchanging a variety of information with an operation monitoring terminal unit and transmitting a driving signal to the actuator 12 on the basis of the information from the sensor 11.
The control network 3 has a duplex configuration so as to enhance reliability of the system, and a PC 4 is also connected to the control network 3. The PC 4 has a function of providing application software such as a function of providing an operator with a variety of information necessary to control and monitor the entire process control system on the basis of the information from the controller 2, an operation monitoring function for making appropriate instruction and management to respective system constitutional elements on the basis of the information and a device managing function for managing repair and maintenance conditions and the like of various devices.
The PC 4 is provided with a dedicated Network Interface Card (hereinafter, also referred to as NIC) 41 for connection to the control network 3, an interface NIC I/F 42 for NIC and the like, as hardware. In the PC 4, an OS 43, a variety of application software 44 and the like are stored as software.
In the meantime, the control network 3 is connected with a plurality of PCs 4 so as to form a PC group. However, in FIG. 3, only one PC 4 is shown.
From standpoints of easy procurement, low cost, technology innovation and the like, a universal PC is used as the PC 4 configuring the PC group, and MS-Windows (registered trademark) and the like having high universality are used as an OS.
The efforts to establish the control network 3 by the universal Ethernet (registered trademark) have been also made. In particular, a process control system of a duplex configuration is adopted so as to secure the high reliability.
The transmission standard of the general TCP/IP communication that is to be used for the Ethernet does not have a real-time property, which is required in the process control system.
The ‘real-time property’ described here is to guarantee secure implementation of predetermined processing within a defined time period. For example,
1) A communication response among a plurality of stations connected on the same network is within a defined value (for example: 5 ms) and
2) In the duplex network, a switching time from an operation-side to a standby-side is within a defined value (for example: 5 ms).
Therefore, in order to perform real-time communication on the Ethernet, a technology relating to ‘real-time plant network system Vnet/IP (registered trademark)’ for process automation based on Ethernet of 1 Gbps is developed and used, as disclosed in Non-Patent Document 1.    [Non-Patent Document 1] Koji Demachi et al., ‘Real-time plant network system Vnet/IP’, Yokogawa technical report, Yokogawa Electric Corporation, Apr. 20, 2005, Vol. 49, No. 2 (2005), p. 37-40
A dedicated interface card for Vnet/IP is required so as to perform Vnet/IP communication in a universal PC. However, since each dedicated interface card for Vnet/IP mounted on each PC has a master property of switching the redundant network 3, it is not possible to provide a plurality of interface cards on the same station address.
In the meantime, the generation changes of the universal PC, a variety of components thereof and the OS such as Windows (registered trademark) are made every few years, so that the cost performance largely increases. On the other hand, the supply of the old-generation product is stopped in many cases.
In the meantime, the process control system is necessarily required to continuously operate over the plant lifetime of about 30 years. The application software such as the operation monitoring function is required to have the operability and function as usual during the operating time period even when the generation changes of the OS and the like are made, because of the habit and education of the operator, the preservation of the know-how and the like.
FIG. 4 depicts a configuration of an example of the process control system of the related art for coping with the above needs, and the parts common to FIG. 3 are denoted with the same reference numerals. In FIG. 4, a virtualization unit 45 is provided between the hardware including the NIC 41 and the NIC I/F 42 and the OS 43.
While the virtualization unit 45 has a function of emulating the variety of hardware in a software manner, a throughput may be lowered. In the process control system placing great importance on the real-time property, it is important to take measures against the lowering of the throughput.
Also, as the technology of the universal PC is innovated, the universal I/F of the PC also evolves. As the universal I/F evolves, it is difficult to purchase a universal PC corresponding to the old-generation universal I/F. In order to cope with the new evolved universal I/F, it is necessarily required to again develop a dedicated interface card on many occasions in correspondence to the evolution of the universal I/F of the PC because it is not possible to continuously use the same dedicated interface card during the plant lifetime
Also, when the universal Ethernet card is used, for example, it is necessary to perform switching processing and the like on the OS, upon occurrence of an abnormality, so that it is not possible to satisfy the need of the real-time processing such as prompt switching.